1. Field of the Invention
This invention relates generally to internal combustion engine preconditioning and testing systems, and more particularly, to an arrangement that exercises and burnishes intake and exhaust valves in their respectively associated seats in a cylinder head to improve the quality of the seal therebetween and that identifies valves that do not provide an adequate seal.
2. Description of the Related Art
There is a need in the engine assembly industry for a system that permits leak testing in an engine head assembly with sufficient resolution to determine whether a problem exists, or is expected to exist, in the mating valve surfaces. The performance of a leak test in a production environment applied to engine intake and exhaust valves is difficult. A primary reason why valves and seats do not form adequate seals is that contaminants and small surface imperfections exist between the mating surfaces. Usually, minor imperfections are quickly burnished out during normal engine operation and result in no long term quality issues. However, the early assembly imperfection and contaminations permit excessive leakage through the valve assembly. Engine manufacturers cannot in practice fail all of the assemblies that have this leakage condition during the manufacturing process as such would require failure of many leaking valve assemblies that would correct themselves during normal engine operation.
The prior art has sought to achieve a solution to this problem by constructing equipment that uses a conventional engine cam and/or hydraulics to exercise a valve assembly prior to a leak test. This action burnishes-in the valves to an extent that permits a more accurate leak test to be performed. It is a problem with known equipment, however, that the extent of burnishing is directly proportional to the load experienced by the mating valve surfaces and the amount of xe2x80x9chitsxe2x80x9d (or cycles) that the valve assembly is permitted to experience during the burnishing operation. In a known hydraulic system, the xe2x80x9chitsxe2x80x9d in the mating valve seats are not of optimum amplitude as a result of the amount of mass and fluid that has to be returned by an engine valve spring before it contacts the seat. It is also a disadvantageous characteristic of known arrangements that the amplitude of the xe2x80x9chitsxe2x80x9d is minimized since an engine cam that is used to drive the valves is optimized to minimize the valve loading.
There is a need, therefore, for an arrangement that quickly exercises the engine valves to achieve an amount of burnishing adequate to permit a valid and accurate leak test to be performed thereafter. The amplitude of the xe2x80x9chits,xe2x80x9d however, should not be so large as to damage the valves or the seats in the cylinder head.
It is, therefore, an object of this invention to provide an arrangement that exercises and burnishes engine intake and exhaust valves so that adequate leak testing can be conducted immediately thereafter.
It is another object of this invention to provide an arrangement that improves the quality of the seals effected between engine valves and their respective seats.
It is also an object of this invention to provide an engine valve exercising arrangement that can operate over a broad range of operating speeds.
It is a further object of this invention to provide an arrangement that quickly exercises the intake and exhaust valves of an internal combustion engine with the application of valve loading that is greater than that which is achieved by a conventional valve train.
The foregoing and other objects are achieved by this invention which provides, in a first apparatus aspect thereof, an arrangement for seating a valve in valve seat in a first side of a cylinder head of an internal combustion engine. The valve is of the type having a valve sealing portion for communicating with the valve seat and a valve stem that is accessible on a second side of a cylinder head. In accordance with the invention, a source of reciprocating motion effects reciprocation along a predetermined linear path of reciprocation. A first jig defines a predetermined location of the cylinder head in relation to the source of reciprocating motion. A coupling arrangement couples the source of reciprocating motion to the valve in the cylinder head. Additionally, a second jig is provided for communicating with the first side of the cylinder head and defining a test chamber that surrounds the valve seat and the valve sealing portion.
In one embodiment of this aspect of the invention there is provided a ram for applying a force to the second jig and urging same into sealed relation with the first side of the cylinder head. In some embodiments, the ram also urges the cylinder head against the first jig whereby it is maintained in fixed relation with respect to the source of reciprocating motion.
A valve rotating arrangement, which may be incorporated in the cylinder head, causes the valve to rotate with respect to the valve seat as the valve is displaced reciprocatingly along its respective displacement path. Such rotation enhances the valve seating in the valve seat of the cylinder head.
The test chamber is provided with a fluid input to permit delivery thereto of a fluid whereby a pressure retention test is performed in the test chamber. In one embodiment, the fluid input is in the form of a air inlet. There is additionally provided a pressure sensor that produces a signal responsive to the pressure in the test chamber.
One or more sealing elements are provided for sealing apertures in the cylinder, as would be the case with a fuel injector of a Diesel engine.
In an embodiment of the invention, the source of reciprocating motion includes a source of rotatory motion for rotating about an axis of rotation. An eccentric cam is coupled to the source of rotatory motion and arranged to rotate therewith. A linear drive arrangement has a first end thereof arranged to communicate with the valve stem of the valve, the linear drive arrangement and the valve being displaceable along parallel respective displacement paths. Additionally, a cam follower is coupled to the eccentric cam and to the linear drive arrangement. In this manner, the linear drive arrangement is urged into reciprocating linear motion in response to the rotation of the eccentric cam.
In a highly advantageous embodiment of the invention, the eccentric cam is formed of a closed, substantially annular protuberance extending substantially axially parallel to the axis of rotation. The substantially annular protuberance has radially inward and radially outward facing surfaces. In this embodiment, the cam follower is formed of first and second cam follower rollers that are arranged substantially parallel to one another and to communicate with respective ones of the radially inward and radially outward facing surfaces of the substantially annular protuberance.
In a further embodiment of the invention, the linear drive arrangement is formed of a reciprocating element that is coupled to the first and second cam follower rulers. The reciprocating element has a first predetermined cross-sectional configuration. A stationary guide way is provided with a predetermined cross-sectional configuration that corresponds to that of the first predetermined cross-sectional configuration of the reciprocating element, and thereby accommodates same therewithin. In a highly advantageous embodiment, a Teflon(copyright) sheet insert is interposed between the reciprocating element and the stationary guide way for reducing friction therebetween. It has been discovered that this arrangement provides a highly advantageous low-friction reciprocating system that does not require any additional lubricants. In fact, most known lubricants increase the friction between the Teflon(copyright) sheet insert and the reciprocating element. The application of excessive force to the valve stem by the reciprocating element is precluded by a resilient overload element that provides a resilient accommodation of a force that would exceed a predetermined magnitude. The resilient overload element may be in the form of a spring having a resilience characteristic that would protect the valve from excessive or damaging forces.
In a highly advantageous embodiment of the invention, two engine valves are exercised and tested simultaneously. Thus, there is provided a second valve in the first side of the cylinder head of the internal combustion engine, the cylinder head having a second valve seat in the first side thereof. The valve is of the type having a respective valve sealing portion for communicating with the second valve seat, and a valve stem that is accessible on the second side of the cylinder head, as is the first valve. A second eccentric cam is coupled to the source of rotatory motion arranged to rotate therewith. A second linear drive arrangement has a first end thereof arranged to communicate with the valve stem of the second valve, the linear drive arrangement and the valve being displaceable along parallel respective displacement paths. A second cam follower is coupled to the second eccentric cam and to the second linear drive arrangement. In this manner, the second linear drive arrangement is urged into reciprocating linear motion in response to the rotation of the second eccentric cam.
In one embodiment of this dual valve-testing arrangement, the first and second eccentric cams are coaxially coupled to the source of rotatory motion and arranged to rotate therewith. Each of the first and second eccentric cams is formed as a closed, substantially annular protuberance that extends substantially axially parallel to the axis of rotation. Each of the annular protuberances has respective radially inward and radially outward facing surfaces, and are arranged to extend in opposite directions. In a further embodiment, both eccentric cams are coupled to the source of rotatory motion in an out-of-phase relationship with respect to one another.
In accordance with a further apparatus aspect of the invention, there is provided an arrangement for seating a valve in a valve seat in a first side of a cylinder head of an internal combustion engine. As previously indicated, the valve is of the type having a valve sealing portion for communicating with the valve seat, and is further provided with a valve stem that is accessible on a second side of the cylinder head. In accordance with this further aspect of the invention, there is provided a source of rotatory motion for rotating about an axis of rotation. An eccentric cam is coupled to the source of rotatory motion and is arranged to rotate therewith. A first end of a linear drive arrangement is arranged to communicate with the valve stem of the valve, the linear drive arrangement and the valve being displaceable along parallel respective displacement paths. A cam follower is coupled to the eccentric cam and to the linear drive arrangement, such that the linear drive arrangement is urged into reciprocating linear motion long a predetermined linear path of reciprocation in response to the rotation of the eccentric cam. A first jig defines a predetermined location of the cylinder head in relation to the source of reciprocating motion. A second jig communicates with the first side of the cylinder head and defines a test chamber that surrounds the valve seat and the valve sealing portion. A force is applied to the second jig by a ram that urges same into sealed relation with the first side of the cylinder head. Fluid is then introduced via a fluid input to the test chamber, whereby a pressure retention test is performed in the test chamber.
It is noteworthy that the reciprocating motion of the linear drive arrangement is controlled in both directions. That is, the valve springs are not relied upon to urge the linear drive arrangement during the closing stroke of the valve. In this inventive arrangement, therefore, significantly higher valve loading can be achieved over conventional cam and hydraulic lifter arrangements, where the valve return spring must additionally urge a significantly increased mass, as well as oil in the lifters, during the return (to closed state) stroke. This additional loading imposed by the valve train components in conventional arrangements reduces the return rate of the valve, and consequently the time period required to exercise the valve to achieve an adequate break-in, or burnishing, of the valve and the valve seat, whereby a meaningful leak test can be performed, is significantly extended.
In one embodiment of the invention, the eccentric cam is as previously described having a substantially annular protuberance extending substantially axially parallel to the axis of rotation. The substantially annular protuberance has radially inward and radially outward facing surfaces. Further in this embodiment, first and second cam follower rollers are arranged substantially parallel to one another and to communicate with respective ones of the radially inward and radially outward facing surfaces of the substantially annular protuberance. The linear drive arrangement is provided, in one embodiment, with a reciprocating element that is coupled to the first and second cam follower rollers, the reciprocating element having a first predetermined cross-sectional configuration. A stationary guide way has a predetermined cross-sectional configuration that is configured to correspond to the first predetermined cross-sectional configuration, whereby the reciprocating element is accommodated within the stationary guide way. Lubrication is effected as previously described by the interposition of a Teflon(copyright) sheet between the reciprocating element and the stationary guide way.
The communication between the linear drive arrangement and the valve stem is such as to permit the valve to rotate by operation of a valve rotating arrangement. Thus, as the valve is reciprocated, it is also rotated, thereby enhancing the seal between the sealing portion of the valve and the seat in the cylinder head.
In accordance with a method aspect of the invention, there is provided a method of seating a valve in a valve seat in a first side of a cylinder head of an internal combustion engine. The valve is of the type having a valve sealing portion for communicating with the valve seat. Additionally, the valve has a valve stem that is accessible on a second side of the cylinder head. In accordance with the invention, the method includes the steps of:
controlling a substantially linear reciprocating motion of a reciprocating drive arrangement;
coupling the valve to the reciprocating drive arrangement;
rotating the valve with respect to the valve seat; and
testing the seal between the valve sealing portion and the valve seat in the first side of the cylinder head.
In one embodiment of this method aspect of the invention, prior to performing the step of controlling there is provided the further step of positioning the cylinder head in fixed relation to the reciprocating drive arrangement. In an advantageous embodiment, the step of positioning the cylinder head comprises the further the further step of forming a test chamber on the first side of a cylinder head. In addition, the step of positioning the cylinder head includes the further step, in one embodiment, of operating a ram to apply a force to the cylinder head and against a positioning jig.
Testing is effected by the step of pressurizing the test chamber with a fluid to determine whether leakage is present between the valve sealing portion and the valve seat in the first side of the cylinder head. The pressure in the test chamber is monitored over a predetermined period of time.
This method aspect of the invention further includes, in one embodiment, the step of sealing an injector opening in the cylinder head during the step of pressurizing.
In a further embodiment of the invention, the step of controlling includes the further steps of:
operating a source of rotatory motion;
rotating an eccentric cam in synchrony with the source of rotatory motion; and
constraining a cam follower arrangement to move reciprocatingly in response to the step of rotating an eccentric cam. In a further embodiment, the step of constraining includes the step of interposing a Teflon(copyright) lubricating sheet between stationary and reciprocating portions of the reciprocating drive arrangement.